I. Field of the Invention
The present invention relates generally to the smelting of iron ore or iron oxides and, more particularly, to a composition and method for the production of metallic iron from iron ore without agglomerating the feed stock.
II. Related Art
In the last few years methods have been developed for what is known as direct reduction or direct iron production, also referred to as the production of iron nuggets from iron ore as described for example in the following journal articles:
Anameric B. and Kawatra S. K, Transformation Mechanisms of Self Reducing Fluxing Dried Greenballs into Pig Iron Nuggets, Presented at 2007 SME Annual Meeting, 2007 (c).
Anameric B. and Kawatra S. K., Laboratory Scale Investigations on the Formation of Pig Iron Nuggets, Submitted for publications in ISIJ International, January 2007 (b).
Anameric B. and Kawatra S. K., Conditions for Making Direct Reduced Iron, Transition Direct Reduced Iron and Pig Iron Nuggets in a Laboratory Furnace—Temperature Time Transformations, Submitted for publication in Minerals and Metallurgical Processing, May 206 (c), Preprint no MMP-06-027.
Anameric B. and Kawatra S. K., Pig Iron Nuggets Versus Blast Furnace Pig Iron, Presented at TMS Fall Extraction and Processing Meeting. Proceedings of the Sohn International Symposium, San Diego, Calif., Vol. 5, 2006 (b), pp. 136-156.
Tsuge O., Kikukuchi S., and Tokuda K., Successful Iron Nugget Production at ITmk3 Pilot Plant, 61st Ironmaking Proceedings, Nashville, Tenn., 2002.
Kobayashi I., Tanigahi Y. and Uragami A, A New Process to produce Iron Directly From Fine Ore and Coal, Iron and Steelmaker, Vol. 28 No. 9, 2001, pp. 19-22.
Eisele, Timothy C. and Kawatra, Surendra Komar, U.S. Pat. No. 7,632,330, Issued Dec. 15, 2009.
All of the above described processes include mixing the iron ore concentrate, reductant and flux and then agglomerating the mixture by pelletizing or briquetting usually with drying, heating or baking prior to placement of the mixture into a furnace.
The current practice of agglomerating the feedstock mixtures prior to being fed to iron nugget making furnaces requires special compacting equipment and binders and adds to the cost, efficiency and complexity of this operation. In addition, current practice either does not produce separately usable excess gases or does not capture and utilize such additional gases produced during the reduction process for electrical generation or other energy or reduction uses. Current practice does not provide a direct reduction process that can smelt manganiferous ores to produce either a manganese containing iron nugget or separately a high iron, low manganese nugget and a manganese rich slag. Current practice does not provide a direct reduction process that can produce a high iron, low titanium iron nugget and a titanium rich slag, using biomass as a reductant from titaniferous ore or concentrates.
In view of these and other deficiencies in the prior art, it is one object of this invention to provide a method to produce iron slabs or nuggets by feeding a mixture of iron ore concentrates or iron oxides, reductant and flux into the reduction furnace in a loose or un-agglomerated, un-pelleted or un-briquetted form, yet enabling the production of high quality, 95-98% iron 1-3% carbon, metallic iron slabs, bars, mini-ingots or nuggets that readily separate from the slag also produced during the reduction process. The capability to produce high quality metallic iron slabs or nuggets without the need to agglomerate the furnace feedstock, greatly reduces the capital and operating cost, by eliminating the pelletizing or briquetting facility, with associated high capital, maintenance, high power requirements and high operating costs. In some cases the product produced directly in accordance with the invention can qualify as a high carbon steel.
Another object is to co-produce a synthetic as (“syngas”) during the production of metallic iron slabs or nuggets from ore. The co-production of syngas provides a source of energy that can be converted to electrical energy that can be used in the processing operation. The syngas can also be a source of heat or energy for other uses.
Still another object of this invention is to provide a composition and method for the production of metallic iron that contains an appreciable amount of manganese, or in the alternative, to produce a metallic iron slab or nugget that has a high iron and low manganese content while, at the same time, producing a manganese rich slag. The manganese rich slag can be further processed to produce commercial grade manganese products.
A further object of this invention is to provide a composition and method for the production of metallic iron slabs or nuggets from an ore or concentrate that contains both iron and an appreciable titanium oxide content, while at the same time producing a titanium rich slag.
The invention also provides a new method of producing an iron nugget or slab from a pelletized, briquetted or loose unagglomerated mixture of titaniferous concentrates biomass in a particulate form and flux. The mixture is processed at 1490° C. for fifteen minutes, which allows the viscous titanium rich slag to separate from the iron nugget to produce a slag that separates cleanly from the iron nugget.
Yet another object is to provide a process as described above in which the slag is readily separated from the metallic iron produced.
A further object of this invention is to provide an improved method and composition for the production of metallic iron in a form that can be conveniently handled and shipped, is stable against oxidation and corrosion, is a suitable feedstock for steel making and foundry operations and is able to utilize a wide variety of readily available, raw materials as well as to enjoy other advantages that will be apparent from the following description.
Yet a further object of this invention is to produce directly reduced iron (DRI) from mixture of loose, un-agglomerated iron ore concentrates or iron oxide together with either a biomass or coal or coke reductant, by processing the feedstock for a shorter time period and a lower temperature than that previously required for the production of iron nugget. Another object of this invention is to utilize biomass as a reductant in the place of coal or coke in a briquetted or pelletized form while processing the feedstock at a lower temperature and for a shorter residence time than required to produce a metallic iron nugget.
These and other more detailed and specific objects of the invention will be apparent from consideration of the accompanying specification claims and drawings which illustrate by way of example but a few of the various ways in which the invention can be accomplished within the scope of the appended claims.